Johanson is well-known nationally as a top Democratic strategist. She managed the campaign of U.S. Sen. Tammy Baldwin, the Wisconsin Democrat who became the first openly gay candidate elected to the U.S. Senate.

Turner previously was a campaign manager for former U.S. Rep. Chet Edwards. In a news release, Davis said Turner had nearly two decades of Texas politics experience "and knows how to win in tough races."

"Karin has been an amazing partner in getting our team up and on their feet. Under her management, we have raised more money, have more donors and have more volunteers than any candidate ever in Texas. I'm grateful for the skills she's brought to us and appreciate the effort she is putting into the transition," Davis said Wednesday in a statement.

Davis said Johanson and Davis will work together to transition the management of the campaign.

"As we make these changes, we will not let up for one second as our aggressive team continues to organize voters in every region of the state and drive the agenda both for our campaign and the campaign of my opponent every single day," Davis said.